Surface acoustic wave (SAW) devices are often used in filtering applications for high-frequency signals. Of particular benefit is the ability to create low loss high order bandpass and notch filters without employing complex electrical filter circuits, which may require numerous active and passive components.
A common filtering application is in the transceiver circuitry of wireless communication devices. The maximum attainable SAW filter bandwidth and achievable minimum Insertion Loss are determined primarily by the piezoelectric properties of the substrate material and the metallization used for the transducers. At the same time choice of proper SAW filter structure is critical to meeting a specific filtering requirements specification. In mobile communications, there is always a need to minimize device insertion loss in order to increase battery life. Secondly, there is a need to decrease costs and minimize size. As such, there is a need for a more efficient technique to implement SAW filters with lower loss and wider bandwidths.
Although SAW filters with lower losses and wider bandwidths can be realized by choosing different materials, aspects like performance over operating temperature range and cost of implementation can be prohibitive.
As such, there is a further need to provide a SAW architecture that will allow wider filter bandwidths while minimizing losses to the signal being filtered irrespective of the substrate material being used. This will allow low cost implementation of improved filters as well as allow for application of current low cost materials with beneficial properties for newer applications.